Eren's Sister (Attack on titan)

Ammy Jaeger had all ways dreamed of going outside the wall with her brother, Eren, her adopted sister, Mikasa , and their friend, Armin until the colossal one appeared. . .
Ammy is 2 years younger than Eren and the others
Warning: This story goes by the episodes within the tv and manga, this will contain spoilers. If you complain there are spoilers I will mute you.